sn/(nan)=[n(a 1+an)/2]/(nan)= a 1/(2an)+ 1/2 = a 1/[2 *(a 1+(n- 1)d)]+ 1/2

When n→∞, (n- 1)d→ addition and subtraction ∞, [2*(a 1+(n- 1)d)]→ addition and subtraction ∞, a1[2 * (a/kloc-0)]

Arithmetic progression is a common series. If a series starts from the second term, the difference between each term and its previous term is equal to the same constant. This series is called arithmetic progression, and this constant is called arithmetic progression's tolerance, which is usually represented by the letter D.

The general formula is: an = a 1+(n-1) * D. The first term is a1,and the tolerance is D.

The first n terms and formulas are: sn = a1* n+[n * (n-1) * d]/2 or Sn=[n*(a 1+an)]/2.